1. Field of the Invention
The present invention relates generally to a safe use of a gas appliance, and more particularly, to a method of testing and compensating gas supply for safety.
2. Description of the Related Art
Home gas appliances, such as gas water heater, gas stove, and other appliances which burn gas, have a hose connected to a gas supply. The gas supply provides the gas appliance gas, and the gas is mixed with air in the gas appliance in a proper ratio (a target air fuel ratio, A/F ratio) for burning. With a low A/F ratio, which means there is more air in the mixed gas, it is difficult to burn the mixed gas, while with a high A/F ratio, there is more gas in the mixed gas, hence it is easy to have an incomplete burning function, and that will generate carbon monoxide, which is toxic to human. To have a safe use of the gas appliances in the market, the manufacturers had preset proper gas flow rates for various types of gas appliances. It assumes that the gas supply has a constant pressure to provide a proper and constant gas flow rate to the gas appliance by choosing a hose with a suitable cross section. As a result, it will have a mixed gas with an optimal A/F ratio in the gas appliance.
However, abnormality of the A/F ratio is hard to detect when the gas appliance is in use. Even through the user is aware of gas or carbon monoxide in the air, he/she might think that it is caused by malfunction of the gas appliance rather than the improper A/F ratio of the mixed gas, thus when a technician changes some parts inside the gas appliance, it still doesn't fix the problem. In other words, some problems of the abnormal burning activity of the gas appliance is caused by gas supply, rather than the gas appliance itself. Too high or too low pressure of the gas supply will cause an improper A/F ratio of the mixed gas, and that is the key reason to the abnormal burning activity of the gas appliance. However, the abnormality of the gas supply is hard to detect, and the user often put the blame on the gas appliance when it is functioning abnormally and can't be fixed. It is common to think that there is a problem with function of the gas appliance when accidents happen, even though it is often not the case.